Once you get a drowning man out of the water, if he isn' t breathing, you must first________.

A．If a man does not breathe for minutes, his brain will be completely destroyed.
B．If you see someone drowning, you must give him mouth-to-mouth breathing.
C．Don' t stop pressing his chest, if the drowning man starts breathing again.
D．When pressing, you can do it as hard as you can.

A．how to save people out of the water
B．how to give first aid to people who are drowning
C．how to mouth-to-mouth breathing
D．how to save a child from a river